The Environmental Protection Agency (“EPA”) has finalized a new evaporative emission control program, scheduled to take effect in the 2011 model year, that will be focused on reducing hydrocarbon, nitrogen oxide, and carbon monoxide emissions from marine spark-ignition (“SI”) engines. In particular, the new EPA standards include requirements for controlling “permeation” and “diurnal” emissions from marine vessels, as well as permeation and running loss emissions from small SI equipment.
The term “evaporative emissions” refers to hydrocarbons released into the atmosphere when gasoline or other volatile fuels escape from a fuel container. In recent years, manufacturers of boats and other vehicles have begun migrating from metallic, e.g., aluminum, fuel tanks to fuel tanks made of a plastic compound. The plastic tanks, in comparison to the metallic tanks, are lighter, easier to install, have a low manufacturing cost, and have been found to be acceptably durable. Unfortunately, the primary source of evaporative emissions from non-road gasoline engines and equipment is known as “permeation,” which occurs when fuel penetrates the material used in the fuel system and reaches the ambient air. This is especially common through rubber and plastic fuel-system components such as fuel lines and fuel tanks.
Diurnal emissions are another source of evaporative emissions. Diurnal emissions occur as the fuel heats up due to increases in ambient temperature, which causes the liquid fuel to evaporate into the vapor space inside the tank. To protect the tanks from this pressure and prevent pressure buildup, most tanks are provided with vents. The evaporating fuel therefore drives vapors out of the tank through the vent and into the atmosphere. When the ambient temperature cools, e.g., during the night, the fuel vapor once again condenses within the tank.
Running loss emissions are similar to diurnal emissions except that vapors escape the fuel tank as a result of heating from the engine or some other source of heat during operation, rather than from normal daily temperature changes.
All fuel-vapor emissions have been proven to be harmful to humans, as well as to the environment. Therefore, the reduction and control of fuel-vapor emissions remains a concern of the marine industry and is now a requirement by the EPA.
One prior-art attempt to reduce diurnal emissions utilizes a filter, e.g., carbon particles inside a canister-shaped package, which is provided in series with an aeration line connecting the interior of the fuel tank with the environment. While this system reduces emissions for a short time, it has been found that the carbon particles lose their filtering ability when placed into direct contact with fuel and/or water, which is a frequent occurrence with the prior-art design during normal operation of the boat. Attempts have been made to place liquid separator devices between the fuel holding area and the filter, but because fuel still enters the line as it splashes within the tank, these devices are unable to completely prevent the passage of fuel from the tank to the filter.
An additional problem plaguing boat owners as well as the environment is referred to as fuel “spit back.” Spit back occurs during the filling process of a fuel tank and results in fuel being sprayed back at the operator due to a pressure build-up within the tank, which pressurizes the fuel fill line. When the operator removes the fuel pump, fuel splashes out of the fill line. This result is not only harmful to humans and the environment, but creates a serious and dangerous potential for explosion. For boats that are subject to the new diurnal standards, they must also be designed and built such that operators can reasonably be expected to fill the fuel tank without spit back or spillage during a fueling event.
Therefore, a need exists to overcome the problems with the prior art as discussed above.